Apparatus for coating the face plate of a cathode-ray tube envelope



N. D.Y-LEVIN 2,858,797 APPARATUS FOR COATING-THE FACE PLATE 0F A CATHODE-BAY TUBE ENVELOPE Nov. 4, 1958 4 Sheets-Sheet 1 Filed July 26, 1957 IN VEN TOR.

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APPARATUS FOR comma THE FACE PLATE 0F A CATHODE-RAY TUBE ENVELOPE 4 Sheets-She et 5 Filed July 26, 1957 INVENTOR. Wai /Ian D. Levin BY z Oz ivrney United States PatentO APPARATUS FOR COATENG THE FACE PLATE OF A CATHODE-RAY TUBE ENVELOPE Nathan D. Levin, Skokie, Ill., assignor to The Rauland I This invention relates in general to cathode-ray tubes and in particular to apparatus and techniques for applying an organic film to the exposed luminescent screened faceplate of cathode-ray tubes.

Preparatory to the aluminizing process in the manufacture of aluminized cathode-ray tubes, a lacquer film is applied to the prepared luminescent screen affixed to the inside surface of the envelope faceplate. This lacquer film serves as a foundation upon which aluminum vapor can be deposited and must be so applied as to form a uniform and taut base if the subsequently deposited aluminum is to provide a mirror-like backing for the luminescent screen.

A conventional lacquer filming method is based on a flotation process which utilizes a water column upon which lacquer is deposited. Subsequent decantation of the water permits the lacquer film to, adhere to the luminescent screen. An obvious shortcoming of this process is the time consuming element. Another known lacquer filming process involves the use of stationary spraying apparatus in conjunction with a mechanism which rotates the cathode-ray tube envelope while the lacquer is sprayed on to its luminescent surface. In practicing this method, rotating the envelope is necessary in order to distribute the lacquer uniformly over the luminescent screen. This spinning requirement raises difficulties in the adaptation of such a method'to automation activities since the individual cathode-ray tube envelopes must be positioned upon the spinning mechanism or otherwise disassociated from the conveyor which transports the envelopes during the manufacturing process prior to the lacquer spraying operation;

In accordance with the invention, therefore, it is a primary object to provide a novel apparatus for applying an organic film to the luminescent screened surface of a cathode-ray tube envelope.

It is likewise a principal object ofthis invention to provide an improved method of applying a uniform organic film to the luminescent screened surface of the cathode-ray tube envelope. I

It is also an object of this invention to provide novel lacquer filming apparatuswhich renders unnecessary any manipulation of the cathode-ray tube envelope during the filming operation.

It isa corollary object of this invention to provide lacquer filming apparatus amenable to automation.

Another important factor to be considered in spray filming techniques concerns the lacquer material itself, which because of itsinherent volatility and tackiness poses handling and sealing diificulties. It is thus apparent that in addition to managing the envelope, due consideration must be accorded the materials utilized as well as the storage and dispensing thereof. I

Accordingly, it is a further object of this invention to provide spray filming apparatus which obviates the requirement of complex lacquer seals.

In accordance with the present invention, an apparatus is provided for applying, an organic' film to the exposed 2,858,797 Patented Nov. 4, 195$ 2 H surface of a luminescent screen affixed to the face plate of a cathode-ray tube envelope which includes means for supporting the envelope in a fixed position with its axis substantially vertically oriented and with its face plate uppermost. Means for conveying a filming solution are provided whichcomprise a' pair of coaxially' disposed conduits extending vertically into the envelope from below. A ring shaped reservoir for containing a supply of film liquid is rotatable with the conduits while a supply of compressed gas is coupled to the outer conduit. The upper extremity of the outer conduit mounts a'fixed nozzle which communicates with both of the conduits. The apparatus includes means for rotating the reservoir together with the conveying means around the axis of the conveying means for producing a rotating spray of atomized organic film solution within the envelope which spray is directed towards the luminescent screen. 5 The features of the present invention which are be"- lieved to be novel are set forth with particularity in the appended claims. The organization and manner of operation ofvthe' invention, together with further objects and advantages thereof, may best be understood by reference tothe following description taken in connection with the'accompanying drawings, in the several figures of which like reference numerals identify like Figure 4 is a sectional view of the nozzle arrangement utilized'in the principal embodiment;

Figure 4a is a cross-sectional view takenalong the line 4a-4a of Figure'4;

' Figure 5 is an end view of the nozzle arrangement taken along the line 5-5 of Figure 4; t

Figure 6 is an oblique view of the nozzle arrangement taken along the line 6--6 of Figure 4;

Figure 7 is a side' elevation view, partly in section, of an alternate embodiment of the invention;

Figure 8 is a sectional view of the nozzle arrangement utilized in the alternate embodiment;

Figure 8a is a cross-sectional view taken along the 8a8a of Figure 8; and

Figure 9 is a top view of the cathode-ray tube envelope depicted in Figures 1 and 7.

The principal embodiment of Figure 1 includes a table 10 which carries a rotatable support driven by a drive motor 11 that is coupled through a gear box 12 to a shaft 13 which is journalled within the bearing 14 and fixed to a driving pulley 15. Pulley 15 is coupled to a centrally located driven pulley 16 through a drive belt 17 Driven pulley 16 mounts three planetary bearings 18, more clearly shown in Figure 2,-which are' positionably mounted thereto by conventional threaded bolt fasteners 19 in conjunction with spacers 20. A multi-apertured plate 21 receives fasteners 19 and in cooperation with driven pulley 16 aligns planetary bearings 13. Bearings 18 communicate Withthe race surface 22 of a collar 23 whichis secured by screw fasteners 24 to the surface of table 10.

Depending from driven pulley 16 are a plurality of spaced internally threaded couplers 25 secured to pulley 16 by nut fasteners 26. Attached to couplers 25 are a pair of support arms 27 (only one shown in Figure 1), and an elongated support and driving arm 28. Support arms 27 and driving arm 28 are fastened to the inner periphery of a ring-shaped reservoir 29 which has a sump 30, a feed pipe 149, a filler neck 31, and a cap 32. The lower extremity of arm 28 sustains a circular member 33,

line

a nozzle 55 which comprises an atomizer.

better shown in Figure 3, which is engageable with a bifurcated drlven lug 34. An insulator 35 carried by lug 34 has a pair of slip rings 36 which communicate with :a pair of resiliently mounted contacts 37 that can be energized via the electric power cable 38 from a source .-of electric energy (not shown). Slip rings .36 are elecztrically connected by a conductor pair 39 to a solenoid :40 which is operably coupled to an actuating crank 136 associated with a spray gun 51 which can be of a conventional type.

Driven member 34 is releasably secured by a convensupport member 41. Member 47 communicates with a T-connector 48 through axial bore 137. T-connector 48 -is coupled to an air pressure regulator 49 and to the control valve 112 associated with solenoid 40. Tubing .50 connects pressure regulator 49 through a T-coupler Y 138 to reservoir 29 and to an air pressure chamber (not shown) of spray gun 51 while tube 52 pipes a filming --lacquer 53, which can be isobutyl methacrylate, to a fluid chamber (likewise not shown) of gun 51.

A coaxial extension 54, demountably secured to gun 51 by a collet 148, is terminated at its upper extremity by A notched clamp 56 (best shown in Figure 2) is pivotally secured to plate 21 by a fastener 57. A holding bar 58, pivoted in like manner to a pin 139 and adjustably secured by a wing nut 59, in conjunction with clamp 56 rigidly secures extension 54. A second wing nut 60 anchors clamp 56' to plate 21.

The uprights 61, fastened to surface 150 of table 10,

and which mount an apertured guide plate 62 which in turn carries the demountable uprights 63. Uprights 63 are terminated by a ring 64 which supports and vertically orients a cathode-ray tube envelope 65 having a prepared luminescent screened surface 66.

Vertically positionable upon supports 61 is a drain pan 67, which includes a deflector pad 68, centrally disposed about extension 54. Pan 67 is positionably secured by conventional fasteners 69. A water supply inlet 140 (source not shown) is terminated by a control valve 70 -'and provides a constant wash for pan 67. An outlet end of inner conduit 73 and is in contact with the inner surface of conduit 72 thereby attributing a measure of rigidity to coaxial extension 54. Shoulder 75 is provided with longitudinal openings 76 (better shown in Figure 4a) which communicate between an annulus 77 and the included space between conduits 72 and 73. An insert 78 has a threaded portion 79 at its lower extremity for attachment to a correspondingly threaded inner surface of conduit 73. Insert 78 maintains a conical portion 80 at its upper extremity and includes a tapered channel 81 for communicating at its upper end with the central bore 82 in nozzle 55 and at its opposite end with conduit 73. The base 83 of nozzle 55 is seated upon a gasket 84 and is demountably secured within the crown 85 which terminates outer conduit 72 by a collar 86. The conical portion 80 of insert 78 in conjunction with the inner surface of nozzle base 83 defines a passage 87 be tween annulus 77 and bore 82. Preferably, nozzle 55 is provided with an ofiset portion 88 incorporating an asymmetrical discharge orifice comprising a pair of oblique walls 89 (detailed in Figures 5 and 6) which terminate bore 82 of nozzle 55, as described and claimed in the copending application of Francis J. Kinsch for Cathode-Ray Tube Filming Apparatus filed concurrently herewith.

In operation, the subject invention contemplates the application of a lacquer film to the luminescent screened surface 66 of a cathode-ray tube envelope 65, by directing a rotating spray of an air-lacquer mixture thereupon. With reference to the above described principal embodiment, it is apparent that upon energization of motor 11, rotational energy is translated through gear box 12, shaft 13, and driver pulley 15 to propel driven pulley 16 via belt 17. Idler bearings 18 which support pulley 16 and plate 21, being confined Within race 22 of collar 23, enable the spray filming apparatus to be rotatably impelled at a controlled velocity. Pressurized air is admitted through rotating seal 46, inlet member 47 and axial bore 137 to regulator 49 and control valve 112.

Regulated air pressure is thus available through tube 50 and T-coupler 148 to reservoir 29 thereby urging lacquer through feed pipe 149 and tube 52 to the fluid chamber of gun 51. Regulated air pressure is simultaneously available to the air chamber of gun 51. It is noted at this juncture that the constituents for spray filming, i. e.,

a supply of filming lacquer 53 and a source of regulated air pressure, are available to the rotating apparatus without employing a rotating lacquer seal.

Accordingly, while the apparatus is rotating, as above described, a spray filming operation is commenced by electrically energizing solenoid 40 from an electrical source (not shown) coupled to solenoid 40 via cable 38, resilient contacts 37, rings 36 and cable 39. The energization of solenoid 40 operates valve 112 permitting unregulated pressurized air to actuate crank 136 of spray gun 51. The actuation of crank 136 simultaneously couples the aforementioned liquid and air chambers of gun 51 to conduits 73, 72, respectively. The internal operation of gun 51 which performs this operation is conventional and well known in the spray gun art and therefore is not detailed here. A conventional presettable mechanical adjustment on gun 51 (not shown) controls the vertical positioning of needle valve 74 within tapered channel 81 thereby determining the lacquer fiow rate from conduit 73 through channel 81 to bore 82.

With reference to Figure 4, it is noted that upon admission to conduit 72, pressurized air passes through openings 76, annulus 77 and passage 87 to confront pressurized lacquer at the entrance to bore 82 in nozzle 55. The juncture of passage 87 and channel 81 comprise, in effect, a volatilization chamber or atomizer which produces a turbulent mixture of air and lacquer for introduction to bore 82. Offset 88 directs the aforesaid mixture obliquely with respect to the axis of tube 65. The

oblique walls 89 which terminate bore 82 comprise an asymmetrical orifice which transforms the air-lacquer mixture into the diverging mist 200, shown in elevation in Figure 1 and in plan in Figure 9. The configuration and density of mist 200 insures a uniform deposit of lacquer film on surface 66 by directing a comparatively heavy stream of air-lacquer mist outwardly toward the periphery of tube 65 while providing a progressively decreasing mist density as the axis of tube 65 is approached. Offset 88 further provides that the upward discharge of mist 200 perceptibly overlaps the geometric center of the tube in order to obviate a blank or nonuniform filmlayer on that area. The deflector pad 68 protects gun 51 and its associated apparatus by diverting excess lacquer to the adjustable drain pan 67 which is provided with a water circulatory system and continually drains to carry oif such excess.

Upon the completion of the spraying operation, de-

energization of solenoid 40 returns crank 136 to its initial position thereby closing the air and liquid chambers of gun 51. It would be but a matter of simple expediency to utilize a conventional timing mechanism to initiate, time, and terminate the above-mentioned spray filming operations in a predetermined sequence in conjunction with drive motor 12 operation to apply lacquer film layers having a high degree of uniformity to cathoderay tube envelopes.

Figure 7 illustrates an alternate embodiment of the subject invention which can utilize substantial portions of the structure comprising the principal embodiment of Figure l. Specifically, and by way of difierence, the apparatus of Figure 7 employs a drive wheel 91 which is secured by a conventional lock screw 92 to the outer rotatable conduit 93 of a coaxial conveyor device 94. Coaxial conveyor 94 further comprises a stationary inner conduit 95 and a displaceable metering pin 96. R- tatable conduit 93 communicates with an air pressure chamber97 which is secured to surface 150 of table e whereas conduit 95 and pin 96 are terminated by a lacquer well 98 in a manner to be more fully described below. Conduit 93 is provided with an upper bearing support shoulder 99 and a lower shoulder 100 for seating the bearings 101, 102 respectively, which bearings comprise rotatable inner races 103 intimately contacting conduit 93 and stationary outer races 104 secured to chamber 97.

A hermetic rotatable air seal comprises a bellows 105, sealed to conduit 93 by a ring 106, and a rotatable lappedsurface bearing 107 depending therefrom and journalled upon a stationary lapped-surface bearing insert 108 supported by a pedestal 109. In order to insure an adequate air seal, rotatable bearing surface 107 can comprise stainless steel whereas stationary bearing insert 108 is preferably of a dissimilar material, e. g., a graphite material. Vents 110 communicate between enclosure 111 of chamber 97 and the space included between rotatable conduit 93 and stationary conduit 95. A source of pressurized air is coupled through a control valve 112 to an inlet fitting 113 fixed to chamber 97. An electrically operated solenoid 114 is operably associated with valve 112.

Lacquer well 98 is hermetically sealed by the lacquer seal 115 to a mounting plate 116 and secured thereto by the conventional screws 117. The mounting plate 116 and an air seal gasket 118 are hermetically sealed to chamber 97 and fastened by bolts 119. The lower extremity of pipe 95 is vented to well 98 and secured within the apertured shoulder 120 of mounting plate 116. The terminus of metering pin 96 is fixed to a diaphragm 121 depending from well 98. An inlet 122 admits lacquer, which can comprise isobutyl methacrylate, under pressure to well 98. An arm 123 pivotally mounted upon a pin 124 is in permanent contact with diaphragm 121 and has a crank element 125 driveably engaged to the displaceable plunger 126 of an electrically operated solenoid 127. A threaded bar 128 provided with a lock nut 129 cooperates with a tab extension 130 of arm 123 to comprise a limit arrangement for metering pin 96.

Figure 8 shows a sectional view of the upper extremity of the conveyor device 94 (including nozzle 55) which illustrates the coaxial structure requirements peculiar to the alternate embodiment of Figure 7. Protruding from In operation the alternate embodiment which utilizes a driving mechanism substantially identical to that described in connection with the principal embodiment similarly directs a rotating spray upon the screened surface 66 of a cathode-ray tube envelope. The driven arrangement, though, comprises merelythe outer conduit 93 of coaxial conveyor 94 which is secured to drive Wheel 91. In order to obviate the requirement of periodically replenishing the lacquer supply in reservoir 29, the alternate embodiment provides for an-external pressurized lacquer source coupled to well 98 which is coupled-to the stationary inner conduit 95 to obviate the requirement of a rotating lacquer seal. With reference then to Figure 7 it is noted that an initiating procedure similar to that described for operation of the principal embodiment, may be utilized, that is, a conventional timing mechanism (not shown) first energizes motor 11 to bring rotatthe inner periphery of rotatable conduit 93 are shelves 131 which support a rotatable bearing 132 of nylon, or other suitable material, provided with longitudinal apertures 133 for communicating between annulus 77 and conduit 93 in a manner similar to openings 76 of shoulder 75 (Figure 4), and, like shoulder 75, afl'ords a measure of rigidity to coaxial conveyor 94. With the exception of bearing 132, which is analogous to shoulder 75 of conduit 73, the manner in which nozzle 55 cooperates with the coaxial conduits 93, 95, is substantially identical to the previously described cooperation between nozzle 55 and conduits 72, 73 of the principal embodiment.

able conduit 93 to a predetermined operating speed. Thereafter electrical energization of solenoid 114 opens valve 112 to admitpressurized air to chamber 97. The

pressurized air is introduced to rotating conduit 93 through vents and conveyed to nozzle 55 in a man ner similar to the like operation described in conjunction with the principal embodiment of Figure 1. Actuation of a second solenoid 127 initiates the flow of pressurized lacquer from well 98 to nozzle 55. Specifically, energizing solenoid 127 displaces plunger 126 which drives crank element so as to pivot arm 123 in a clockwisedirection about pin 124. This pivotal rotation of arm 123 permits metering pin 96 to withdraw from tapered channel. 81. The travel of arm 123 ceases when extension contacts bar 128 which, in comprising an adjustable limit arrangement, determines the flow rate of lacquer through conduit 95 to channel 81. As in the principal embodiment, upon presentation of pressurized quantities of air and lacquer to nozzle 55, a divergent mist 200 is discharged upon surface 66 of a cathode-ray tube envelope 65. Upon completion of the spraying operation, deenergization of solenoid 114 operates valve 112 to seal off the pressurized air-source while de-energization of solenoid 127 retracts plunger 126 and rotates arm 123 in a counter-clockwise direction to seat metering pin 96 within tapered channel 81 thus terminating the flow of lacquer to nozzle 55.

A timing mechanism similar to that suggested in conjunction with the principal embodirnent can likewise be advantageously employed to initiate, time, and terminate the spray filming operations of the alternate embodiment to insure highly uniform lacquer film deposits.

In summary, the subject invention, as embodied in the spray filming apparatus depicted in Figures 1 and 7, avoids the limitations of the prior art by incorporating coaxial air and lacquer conduits which are adaptable to rotatable operation without the requirement of a rotating lacquer seal, thereby obviating the necessity of coping with the inherently disagreeable qualities of lacquer material generally encountered under such conditions. The principal embodiment provides a compact unitary arrangement which employs a conventional spray gun 51 in conjunction with a simplified mechanical coupling and driving arrangement. The alternate embodiment on the other hand provides for a permanent lacquer source and utilizes but a single rotating element, i. e., outer conduit 93. Furthermore in view of the fact that nozzle 55 (as well as uprights 63) admits of facile interchangeability, the application of this novel apparatus to a variety of spray filming operations is enhanced. In obviating the requirement of spinning the cathode-ray tube envelope, simplified adaptation to automation facilities is realizable since the described embodiments of Figures 1 and 7 can be readily positioned upon vertically displaceable platforms to permit insertion of nozzle 55 within a cathode-ray tube envelope. The requirement for repositioning the enve lope upon the spraying apparatus, which is inherent in apparatus taught in the prior art, is avoided; in the appli- 7 cation of'the subject invention to automation activities, the cathode-ray tube envelope need never be disassociated from its conveyor.

The embodiment of Figure 7, and specifically the construction comprising a stationary inner conduit for the lacquer and a rotatable outer conduit for the gas supply thus providing for an independent lacquer source while still avoiding the need for rotary lacquer seals, is the invention of Jerome J. OCallaghan and is described and claimed in his copending application filed concurrently herewith.

While particular embodiments of the invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.

I claim:

, 1. Apparatus for applying an organic film to the exposed surface of a luminescent screen affixed to the face plate of a cathode-ray tube envelope comprising: means for supporting said envelope in a fixed position with its axis substantially vertically oriented and said face plate uppermost; solution conveying means comprising a pair of coaxially disposed conduits extending vertically into saidenvelope from below; a ring-shaped reservoir for containing a supply of filmliquid and rotatable with said conduits; a supply'of compressed gas coupled to the outer one of said conduits; a nozzle fixed to the upper extremity of said outer conduit and communicating with both said conduits; and means for rotating said reservoir and said conveying means about the axis of said conveying means, for producing a rotating spray of atomized organic film solution within said envelope and directed towards, said luminescent screen.

2. Apparatus for applying an organic fihn to the exposed surface of a luminescent screen afiixed to the face plate of a cathode-ray tube envelope comprising: means for supporting said envelope in a fixed position with its axis substantially vertically oriented and said face plate uppermost; solution conveying means comprising a pair of coaxial conduits extending vertically into said envelopefrom below; a spray gun operatively connected to .said conveying means including a ring-shaped reservoir containing a liquid supply of lacquer material; a supply of compressed gas coupled to said spray gun; a nozzle, including a volatilization chamber, fixed'to the upper extremity of the outer one of said conduits and communi' cating with both said conduits; means for operating said spray gun to supply said lacquer material to the inner one of said conduits and said compressed gas to the outer one of said conduits; and means for producing a rotating spray of atomized organic film solution directed towards said luminescent screen including apparatus for rotating sa1d reservoir, sa1d spray gun, and said conveymg means.

References Cited in the file of this patent V UNITED STATES PATENTS 2,644,770 Sadowsky July 7, 1953 

